Generally, the present invention relates to an arrangement for improving availability of services in a communications system, especially a telecommunications system, said system comprising distributed hardware and software components which interact in order to provide services to one or more users.
More specifically the present invention relates to the improvement of such availability of services in all forms of terminal mobility.
Further, the present invention finds specific utilisation in connection with terminal mobility support in distributed systems, and even more specifically the mechanisms for such terminal mobility support in distributed systems.
An open distributed system is a category of distributed systems which are made up of components that may be obtained from a number of different sources, which together work as a single distributed system. The Open Distributed Processing (ODP) model provides an application interface to the distributed system. In distributed computing, this model is called the virtual main frame and is enabled by distributed object technology, the virtual main frame being created from xe2x80x9ccomponentwarexe2x80x9d.
The present invention will be described in the example, non-limiting context of the industry standard or open distributed processing, named Common Request Broker Architecture, CORBA, which in the present case will be used as a platform for test implementations.
In current distributed platforms, such as CORBA, (see Object Management Group, Inc. The Common Object Request Broker: Architecture and Specification, Revision 2.0, July 1995), terminal mobility is not addressed or supported, and hence, cannot be used in the design and implementation of mobile systems.
In current distributed environments, objects can interact with each other completely independent of where they are located, i.e., on the same machine or on different machines. In FIG. 1, the objects CO1 and CO2 are located on two different machines or nodes, N1 and N2, but can still interact as if they are located on the same machine. The DPE (Distributed Processing Environment) is responsible for marshalling the operation request into messages, locating the addressed object, sending the message to the destination node, unmarshalling the request, delivering the request to the addressed object, and returning the results to the requested object. The network used for the transportation and conveyance of an operation request is called kTN (kernel Transport Network) in TINA terminology, (see TINA-C, Engineering Modelling Concepts (DPE Kernel Specifications), November 1994).
The above applies for fixed systems, but not for mobile systems. In mobile systems, there are numerous nodes that are mobile. A mobile node may frequently change the node with which it has a direct link, and may disappear from a node and reappear later at any other node. The topology of a kernel Transport Network for systems containing mobile DPE nodes therefore changes and may also be undetermined in the sense that the connectivity of a mobile DPE node is not ensured unless additional functionality is inserted in the DPE. In such a mobile system, operational interactions are not guaranteed. Accordingly, there is a need for terminal mobility support functions in DPEs.
An object of the present invention is to provide terminal mobility support which solves the problems noted above.
Another object is to provide an arrangement where terminal mobility support is offered in a distributed environment.
Still another object of the present invention is to provide an arrangement enabling the use of a distributed environment in the design and implementation of mobile systems.
The above objects are achieved in an arrangement of the type as stated in the preamble, which according to the present invention is characterised by the features as stated in the present description and the appending patent claims described, illustrated, and claimed below.